Regardless of the precise nature or function of an apparatus in which components are subjected to wear by a material flow, wear causes need for repair and replacement of components and delays in use of the apparatus while one or more worn components is identified, inspected, removed, and replaced. Wear of components adds to the expense of maintaining and operating the apparatus. Such delays, costs, and expenses are compounded if the apparatus in which wear occurs is located at a remote site.
For example, a wide variety of impact crushers are used in commerce to reduce the size of larger earth materials to smaller sized aggregate. The construction industry trades employ a variety of impact crushers to reduce large aggregate to aggregate sizes and shapes required to satisfy construction specifications for mixtures and admixtures of aggregate with cement and other ingredients and for further processing of size reductions, chemical leaching, and other stages of use. The construction industry's use of impact crushers is but one example of the need to reduce wear caused by a materials flow in an apparatus used to effect the size of particles in the materials flow, to make substantially uniform the size of particles in a materials flow, and to prepare materials for further processing.
Generally, impact crushers provide a device for introducing aggregate into a device for crushing the aggregate. Most impact crushers are designed to rely on centrifugal force to disperse large aggregates through the crusher and to impact the aggregate against a wide variety of impact crusher components to break up, reduce in size, and ultimately eject from the crusher, aggregates composed of desired shapes, sizes, and consistency. Intense efforts have been devoted to improvements in the design and construction of components of impact crushers to reduce the cost of acquiring and operating crushers, to enhance wear resistance of the component parts of crushers, and to facilitate rapid replacement of worn parts of crushers to enable the user of crushers to lose the least possible amount of time during which a crusher is inoperative due to worn parts.
Such improvements are exemplified by those shown in U.S. Pat. No. 3,955,767 issued May 11, 1976 and U.S. Pat. No. 4,690,341 issued Sep. 1, 1987. The Hise Patents are instructive on the number and variety of components which may be included in an impact crusher and consequently exposed to wear during operation of an impact crusher. All components of an impact crusher exposed to a material flow of aggregate, as exemplified in the Hise Patents and other impact crushers, are subject to abrasion, decomposition, fracture, friction, impact, pulsation, wave action, grinding, and other actions causing wear to components of an impact crusher is due to the velocity, acceleration and composition of aggregate flows against, across, and around the components during operation of a crusher (collectively, “wear”). For example, an impeller of an impact crusher may receive and hurl aggregate against one or more crusher components generally known in the art as anvils. An impeller of an impact crusher is known to rotate at speeds from about 500 to about 2000 RPM. The rotation of an impeller, in combination with centrifugal force, creates a material flow of aggregate consisting of a variety of sizes and shapes of aggregate being projected at, over, and around many of the components of the crusher. It is significant that persistent wear occurs not just on anvils, which are designed to cooperate with other crusher components in crushing aggregate, but also on any other component of an impact crusher which may be exposed to the aggregate flow during operation of the crusher.
As a result of persistent wear caused by material flows, components of crushers must be replaced. Replacement of components causes “down time” to repair, refit, and replace components. Additional expenses are associated with replacing the worn part or component, inventorying replacement components, and delivering a replacement component to what is often a remote site.
An impeller may include but is not limited to one or more impeller tables, one or more impeller covers, and brackets holding and connecting the tables and covers. An impact crusher may be designed to use shoes attached to an impeller assembly. The shoes, in combination with centrifugal force, hurl and direct an aggregate flow generated by operation of an impeller assembly against one or more anvils located within the crusher.
The face of the prior art shoes are radially oriented with respect to the central axis of the impellers. The impeller shoes change the direction of the material flowing outwardly along the impeller table due to centrifugal force. The accelerating mass of the material applies a substantial force vector normal to the surface of the shoe. The normal force against the surface of the shoe results in high friction and high wear rates of the shoe.
The table section adjacent the shoes are also exposed to continual material flow and, therefore, higher wear rates than the remainder of the table. Further, the central feed section of impact crushers are subjected to higher wear rates.
U.S. Pat. No. 5,954,282 to Britzke et al. discloses an impeller assembly having wear rods made from a hard material press fit into bores formed in the vertical crusher assembly. Such impeller designs with wear resistant rods in the prior art have a flat central feed disc for receiving vertical material flow. Vertical impact crushers such as U.S. Pat. No. 5,954,282 incorporate a flat central feed disc for receiving material from a hopper. Such a design has limited use with respect to the selection of materials that can be employed with the impact crusher. For instance, finer materials such as lime are not adequately fed to the impeller shoes so as to permit proper propulsion of the lime by the shoes against the anvils for disintegration of the lime material.
In U.S. Pat. No. 5,954,282, the matrix of bores are disclosed as being equidistant from axes through the center of the bores. Such insert rod patterns did not take into consideration areas of impeller assemblies that are more prone to wear because they are subject to greater material flow, material flow forces, and material flow loads.
Ackers et al. U.S. Pat. No. 4,090,673 discloses a centrifugal impact rock crusher having a central feed area with a central feed cone. The central feed area is subject to large impact forces that may arise when rock is fed from the central hopper to the centrifugal impact crusher. Feed cones made from a uniform steel alloy as disclosed in U.S. Pat. No. 4,090,673 must be frequently replaced.
What is needed, therefore, is a device for reducing wear of components of apparatus exposed during operation to a material flow. Particularly, what is needed is a device for reducing wear of components of an impact aggregate crusher caused by a material flow of aggregate during operation.
It is an object of the present invention to provide an impact crusher assembly when exposed to material flows during operation of the impact crusher that will increase the wear life of components by resisting wear caused by a material flow across, over, and around the impact crusher assembly.
Still, another object of the present invention is to provide a design for reducing wear of components of impact crushers during operation and a method for manufacturing wear reducing components which are easy to manufacture, use and to practice and which are cost effective for their intended purposes.
These and other objects, features, and advantages of such components for reducing wear by a material flow will become apparent to those skilled in the art when read in conjunction with the accompanying following detailed description, drawing figures, and appended claims.